1. Field of the Invention
The present invention relates to a method for forming a coupling which connects an auto steering wheel with an auto steering shaft. Specifically, the present invention relates to a method for forming an energy absorbing coupling which can absorb the impact energy of a force applied to the steering wheel of an automobile.
2. Description of the Prior Art
In recent years, a contractable shock-absorbing steering shaft which can absorb the impact energy from a force applied to a steering wheel and a steering wheel equipped with a self-aligning mechanism which can change the support direction of the steering wheel and can thereby absorb energy from an applied force have come to be widely employed in auto steering systems.
The energy absorbing mechanism including the self-aligning mechanism is constructed as illustrated, for example, in FIGS. 8 and 9 (U.S. Pat. No. 4,390,193). In this self-aligning mechanism, steering wheel 21 and steering shaft 22 are connected by an energy absorbing coupling 23 which by deforming itself can absorb the energy of an applied force.
In this type of energy absorbing coupling 23, the flange 23a which is a junction to the steering wheel, the deformable member 23b for energy absorption and the boss 23c which is a junction to the steering shaft are integrated. The transitional part from the deformable member 23b to the boss 23c especially is formed from an integral piece by press-drawing.
Generally speaking, when a piece is drawn, a work-hardening of the piece to a certain extent occurs. Thus, when press-drawn, the deformability of the deformable member 23b which absorbs the energy deteriorates through the work-hardening and it is liable to fail in exhibiting the desired stable energy absorbing characteristics. To avoid this trouble due to work-hardening, the use of an annealing process would be necessary. However, annealing would lower productivity and lead to an increased cost in production.